In the transport of perishable products, such as via refrigerated trailers or refrigerated containers commonly called "reefers", it would be desirable to utilize a control arrangement that quickly reduces the product temperature to a pre-selected set point temperature.
It is not possible, however, to have the entire perishable load at the set point temperature with a mechanical refrigeration system, as the refrigeration system draws return air from a served space, passes it through an evaporator coil, and discharges the conditioned air back into the served space. Thus, the return air is warmer than the discharge air when the system is in a cooling mode. The product closest to the discharge point will thus be the coldest, and the product closest to the return point will be the warmest.
Various control arrangements have been used in the prior art in attempts to achieve the best temperature control of a served space, but all seem to suffer at least one disadvantage.